Impact-actuated spring system for producing vibrations in a rotating form



1967 D A. HAUSMANN 3,304,591

IMPACT-ACTUATEf) SPRING SYSTEM FOR PRODUCING VIBRATIONS IN A ROTATING FORM Filed June 8, 1964 2 Sheets-Sheet l INVENTOR, 054 5A? )4. MrwA/mm A r-news)? Feb. 21, 1967 o. A. HAUSMANN 3,304,591 IMPACT-ACTUATED SPRING SYS FOR PRODUCING ONS IN A HOT NG FORM 2 Sheets-Sheet 2 VIBRATI Filed June 8, 1964 INVENTOR. filziiifi, Mai/$14M Irma n1;

United States Patent C) if 3.304591 llMPACT-ACTUATED SPRING SYSTEM FOR PRO- DUCING VIBRATIONS IN A RQTATING FORM Delbert A. Hausmann, Glendale, alif., assignor to American Pipe and Construction Co., Monterey Park, Calif a corporation of California Filed June 8, 1964, Ser. No. 373,454 6 Claims. (Cl. 25-30) This invention relates to a method of producing vibrations in a rotating form or analogous device, and more particularly to a system in which vibration is imparted to the form by the impact of a spring-impelled member, and the spring-impelled member in turn is set in oscillation by impact thereagainst of protuberances judiciously spaced around the periphery of the rotating form. Although described herein specifically in connection with a centrifugal casting process for concrete pipes, the method may be applied to the centrifugal casting of other materials and to other processes requiring simultaneous vibration and rotation.

-Up to the present time, vibration of a rotating form has usually been accomplished with a power-driven highfrequency vibrator or oscillator mounted either directly on the form, or on an external wheel or shoe in contact with the form. The first method is unsatisfactory because of difliculties in transmitting power to the rotating vibrators and because vibrations are produced only at fixed locations on the form. The second method is inefiicient because the frequency of the powered vibrator is generally much higher than the natural frequency of the external mounting system, a condition which suppresses the amplitude of vibration of the contact wheel or shoe. Also, much of the energy supplied to the vibration is lost in viscous and frictional damping in the vibrator mounting system.

The present invention overcomes these difiiculties and inefliciencies of the prior art by providing a stationary,

. tion.

The system of the invention has been empirically proven to be very effective in consolidating both granular and plastic materials, and it will be readily understood by those skilled in the art that it has the following advantages over the prior art: (1) vibrations are transmitted uniformly around the circumference of the form;

(2) any desired impact frequency can be producedby proper selection of spring, wheel assembly weight, and cam spacing; (3) no separate power source is required for the impact system; (4) all energy required to compensate for damping losses is supplied by the rotating form through impact of the cams; (5) the system of this invention transmits a higher percentage of the vibration force to the rotating mass than the systems of the prior art, with a consequent minimal loss of energy through the mounting means to the support frame; and (6) the impact strength is adjustable. In addition, when two impact units are operated against the same rotating form, interference between vibrations from the two sources can be eliminated by locating the cams on one band one-half space out of phase with the cams on the second band. This phase-shift principle can be extended to any number of impact units.

It is therefore the object of this invention to provide a vibrational system for rotating devices capable of distributing vibrations uniformly around the perimeter of 3,3M,5 591 Patented Feb. 21, 1967 the form and transmitting them to the form with a minimum loss of power and maximum amplitude.

It is a further object of this invention to provide a vibrational system for rotating devices in which the motive power is supplied by the rotation of the device itself.

It is another object of the invention to provide a vibrational system for rotating devices in which the vibration is generated by a spring system impelled in synchronism with its natural frequency into continuous half-wave vibrations, by motive means spacedly mounted on the device itself.

It is a still further object of the invention to provide a vibrational system of the type described in which the vibrational force is adjustable.

It is still another object of the invention to provide a system of the type described which permits the use of several independent vibratory units on the same device without mutual interference.

These and other objects of the invention will become apparent from a perusal of the following specification taken in connection with the accompanying drawings, in which:

FIG. 1 is a side elevation of the device of this invention; and

FIG. 2 is a vertical section, partly broken away along line 2-2 of FIG. 1.

Basically, the system of this invention consists of providing cams around the perimeter of a rotating form or similar device. As the form rotates, the cams rhythmically propel a stationary impact wheel away from the form against the bias of a spring. As soon as the camming momentum is expended, the spring rebounds the impact wheel against the form, only to encounter another cam which again propels it away. If the angular velocity of the mold and the cam spacing is so related to the natural frequency of the spring system that the rebound impact occurs precisely as the impact wheel encounters the leading edge of the next following cam, the system sustains its vibrations with maximum efficiency and amplitude and hence with a minimum of camming energy.

Referring now to the drawings, the rotating form is shown at 10. It rests on pairs of support wheels 12 and drive wheels 14, the latter of which are powered by a motor 16. The perimeter of the form 10 carries one or more rings 18, 20 which in turn are provided with cams or protuberances 22. Bearing against the surface of rings 18, 20 and against the cams 22 are impact wheels 24. The impact wheels 24 are biased against the rings 18, 20 by springs 26 contained within the telescoping cylinder members 28, 30. Wedges 32 operated by hydraulic controls 34 permit the impact Wheels to be moved into and out of contact with the form 10. The static biasing force with which the wheels 24 are biased against the surface of the rings 18, 20 can be adjusted by means of the set screw 36.

It will be noted that the cams 22 on ring 18 are displaced by one-half their perimetric interval from those on ring 20. The purpose of this arrangement is to prevent mutual interference between the vibrations set up by the two vibrating systemsi.e., the impact on ring 18 occurs while the wheel 24 associated with ring 20 is out of contact with the ring 20 at the end of its compressive stroke (dot-dash line position of wheel 24 on FIG. 2), and vice versa.

Operation When the spring-mounted impact wheel 24 is brought into contact with the form 10, it is impacted in sequence by each of the cams 22 on the ring 18 or 20. After each impact, the wheel 24 describes one-half cycle of simple harmonic motion as it is driven downward against the spring 26 and rebounded by it against the ring 18 or 20.

6 The period of time required for each impact cycle is a function only of the natural frequency of the spring system and can thus be calculated from the known mass and spring deflection constant of the vibrating system.

For maximum effectiveness, the cams 22 can be spaced so that the frequency with which they pass the impact wheel 24 is exactly equal to twice the natural frequency of the spring system. When this condition is satisfied the impact wheel develops its maximum amplitude and describes a continuous series of half-sine waves with impact occurring between each Wave.

Assuming a rotating form 10 having rings 18, 20 of radius R which in turn carry a series of equally spaced peripheral earns 22 so arranged that each strikes in sequence and with equal force a spring-supported wheel 24 of eifective mass m. Assume the impact delivered by each cam 22 drives the wheel 24 downward at an initial velocity V Neglecting viscous damping and other losses, the change in kinetic and potential energy of m is equal to work done by the spring in opposing motion. Thus V velocity after displacement x,

k pring factor in pounds per inch deflection, and x static spring deflection.

Since and the natural frequency of the undamped spring system is I? w radians per second Equation 1 reduces to At maximum displacement x V=0, and from Equation 4 o n l so that Equation 4 can be rewritten V=w /:c x (6) It is evident from Equations 5 and 6 that, from the time of impact until the wheel 24 again contacts the ring 18 or 20, the sprung mass oscillates in simple harmonic motion for which the displacement at time t is During the rebound portion of the cycle all energy gained by the spring is expended in restoring the original potential and kinetic energy of mass m. Equations 7 and 8 apply, and the period for a complete cycle is thus twice the time given by Equation 9, or

To insure that all actuating cams 22 strike in sequence, the center-to-center cam spacing s should be equal to the peripheral distance traveled during one impact cycle, i.e.,

s=RwT (11) where w is the angular velocity in radians per second, or .from Equation w 3 TREE:

Since the total number of carns is Substitution in Equation 12 gives Example From Equation 2 (21r) w 60 From Equation 13 the number of cams required is =14.l radians/sec.

w,, 88.0 TI2E2(14-1 12.0

Provide 12 cams at l H s 12 -6.02

Most effective operating speed is It will be seen that the present invention provides an extremely simple, efficient and adjustable method of vibrating rotating forms. Obviously, the concept of the invention can be carried out in many different ways, of which the embodiment shown and described herein is merely illustrative. Therefore, the invention is not to be deemed limited by the foregoing description, but only by the scope of the following claims.

What I claim and desire to secure by Letters Patent 1. In combination with a rotating form, a vibrating system comprising: stationary resilient means; impact means carried by said resilient means and resiliently biased thereby into engagement with said rotating form; and means on said rotating form for engaging said impact means to compress said resilient means in synchronism with twice the natural frequency of said resilient means.

2. In combination with a rotating form, a vibrating system comprising: stationary resilient means; impact means carried by said resilient means and resiliently biased thereby into engagement with said rotating form; and equally spaced protuberances around the perimeter of said rotating form arranged to engage said impact means to compress said resilient means in synchronism with twice the natural frequency of said resilient means.

3. In combination with a rotating form arranged to rotate at a predetermined angular velocity, a vibrating system comprising: stationary resilient means, impact means carried by said resilient means and resiliently biased thereby into engagement with said rotating form; and equally spaced protuberances around the perimeter of said rotating form arranged to engage said impact means to compress said resilient means at twice the natural frequency of said resilient means when said form is rotating at said predetermined angular velocity.

4. In combination with a rotating form, a vibrating system comprising: stationary resilient means adjacent each end of said rotating form; impact means carried by each of said resilient means and biased thereby into engagement with said rotating form; and equally spaced camming means around the perimeter of said form adjacent each end thereof arranged to periodically engage said impact means to compress said resilient means upon rotation of said form; the leading edges of said camrning means adjacent one end of said form being perimetrically spaced from the leading edges of said camming means adjacent the other end of said form by one-half the perimetric distance between adjacent camming means.

5. In combination with a rotating form arranged to rotate at a predetermined angular velocity, a vibrating system comprising: stationary resilient means; impact wheel means carried by said resilient means and resiliently biased thereby into engagement with said rotating form; equally spaced cam means around the periphery of said rotating form arranged to engage said impact wheel to compress said resilient means at twice the natural frequency of said resilient means when said form 20 thereby into engagement with said rotating form adjacent the ends thereof; equally spaced cam means around the periphery of said rotating form adjacent each end thereof arranged to engage said impact wheels to compress said resilient means at twice the natural frequency of said resilient means when said form is rotating at said predetermined angular velocity; and means for varying the force biasing said impact wheel against said form; the leading edges of said cam means adjacent one end of said mold being perimetrically spaced from the leading edges of said cam means adjacent the other end of said mold by one-half their perimetric interval.

References Cited by the Examiner UNITED STATES PATENTS 763,329 6/1904 Rowntree 25-41 1,199,997 10/1916 Lienesch 25--3O 1,992,739 2/ 1935 Carrington 25-30 2,703,916 3/1955 Butler 253O FOREIGN PATENTS 4,843/ 26 11/ 1927 Australia. 227,190 3/ 1960 Australia.

25 J. SPENCER OVERHOLSER, Primary Examiner.

G. A. KAP, R. D. BALDWIN, Assistant Examiners. 

1. IN COMBINATION WITH A ROTATING FORM, A VIBRATING SYSTEM COMPRISING: STATIONARY RESILIENT MEANS; IMPACT MEANS CARRIED BY SAID RESILIENT MEANS AND RESILIENTLY BIASED THEREBY INTO ENGAGEMENT WITH SAID ROTATING FORM; AND MEANS ON SAID ROTATING FORM FOR ENGAGING SAID IMPACT MEANS TO COMPRESS SAID RESILIENT MEANS IN SYNCHRONISM WITH TWICE THE NATURAL FREQUENCY OF SAID RESILIENT MEANS. 